1. Field of the Invention
The present invention relates generally to an electric wheelchair for aged persons or the like and, more particularly, to a four-wheeled electric wheelchair propelled by power from an electric motor driven by a battery.
2. Description of the Related Art
In recent years, electric wheelchairs, employing an electric motor driven by a battery, have been developed for the aged with feeble lower limbs and physically-handicapped persons. These wheelchairs run at a walk speed of a human and are thus easy for the aged to drive and may conveniently be used to go out for shopping and visit their neighbors. The electric wheelchairs are used particularly by the aged with weakened lower limbs, because they broaden the sphere of activity of the aged.
Such electric wheelchairs are disclosed, for example, in Japanese Utility Model Publication Nos. HEI 3-80503 and HEI 5-39696. The disclosed electric wheelchairs are of the type having one front wheel and two rear wheels, that is, three-wheeled.
Normally, persons of advanced age have a poor sense of balance and are incapable of instantaneous actions. Thus, the electric wheelchairs are required to provide sufficient stability during travel thereof. However, due to their inherent construction, the three-wheeled electric wheelchairs of the described type have a drawback in that they are unstable during travel thereof.
Four-wheeled electric wheelchairs having two front wheels and two rear wheels are most desired from the standpoint of travel stability. With this in view, the present inventors have proposed such four-wheeled electric wheelchairs in Japanese Patent Publication No. HEI 5-58343 and Japanese Utility Model Publication No. HEI 5-17046.
In the disclosed four-wheeled electric wheelchairs, the tread between the rear wheels is larger than the tread between the front wheels. Correspondingly, the body width at the rear part of the wheelchairs is larger than the body width at the front part of the wheelchairs.
When driving such wheelchairs, drivers constantly look ahead and are thus likely to use the front body width of the wheelchairs as a reference in determining whether they could pass an obstacle such as a curb. Accordingly, where the rear bodies of the electric wheelchairs have a width larger than that of a front body, there is a fear that an obstacle is hit by either of the rear wheels.
Generally, persons of advanced age with weakened lower limbs get aboard the electric wheelchairs from the sideways of the rear parts thereof while supporting themselves by holding onto the seats or their backs in the wheelchair rear parts. Thus, in the electric wheelchairs with their rear body parts projected laterally due to the rear wheels incorporated therein, difficulty is often experienced in getting on and off, because the projected rear body parts do not allow the aged persons to stand or position their legs closely to the wheelchairs. Thus, improvements are desired of the electric wheelchairs in that respect.
Further, when the electric wheelchairs having the larger tread between the rear wheels than the tread between the front wheels make a turn, the distance between the tracks of the inner or turn side front and rear wheels (inner track difference) becomes large, thereby leaving a fear that the turn side rear wheel may hit an obstacle such as a curb in the turn side rear wheel's track. Thus, the electric wheelchairs, when designing for use by the aged, should incorporate improvements made to negate such fear.
Moreover, it is desired that the electric wheelchairs be stable while running and have high maneuverability. For this reason, the electric wheelchairs need to be small-sized.
However, as can be readily appreciated from the foregoing publications, in the rear wheel drive mechanism including a motor and a reduction gear, the motor and the reduction gear are respectively positioned forwardly and backwardly of an axle, thereby increasing the longitudinal lengths of the electric wheelchairs. As an alternative, the motor and the reduction gear may be positioned transversely of the wheelchair bodies but this will increase the widths of the wheelchairs.